while SignagePlayer 4.12 will work with mediaSERVER 4.20, you will not get all of the feature set in player (such as transitions etc).So it is always recommended to run latest version of SignagePlayer... (4.20 is latest release player).

The current version which works at customer side is 4.12 (mediaserver not cloud) will be compatible with signage players which are 4.20? I got the info from chatsupport that both products Media Server and signageplayer should be the same version in order to work correctly.